This application claims the priority of Swiss patent application 2983/96, filed Dec. 12, 1996, the disclosure of which is incorporated herein by reference in its entirety.
1. Technical Field
The invention relates to a position-measuring device.
Devices of this type are especially used as input or operating apparatus, e.g. for operating screen graphics (e.g. for CAD systems) and computer animations, for controlling robots, for moving parts of tool and measurement machines (spindle boxes and measuring heads), as sensors or for controlling remote controlled probes and surgical instruments.
2. State of the Art
In conventional devices, where displacements with three or even five to six degrees of freedom are measured, complicated measuring electronics are required, which makes the devices more expensive and unwieldy, or simpler measuring electronics are used, which, however, lead to unsatisfactory ergonomic properties. Examples of such devices are given in U.S. Pat No. 4,811,608, EP 244 497, EP 240 023 and EP 235 779. In all these devices, optical, mechanical or electrical sensors are required, which must additionally be housed in the device and lead to a correspondingly complicated setup.
Hence, it is an abject of the invention to provide a device of the type mentioned above that avoids these disadvantages.
Hence, parameters of the elastic coupler are measured directly, such as forces, electrical properties, etc. In this way, separate sensors can be dispensed with or be designed in very compact manner, since the coupling device itself forms at least a part of the sensors.
In a preferred embodiment several inductivities of the coupler, or of parts of the coupler are measured. Thus, for instance, the inductivity of springs of the coupler depending on the dilatation is measured.
Further electric parameters that can be measured are the electric resistance or the capacity of parts of the coupler.
Since three or more parameters must be measured for detecting the position or orientation with three or more degrees of freedom, these parameters are preferably measured sequentially, such that the individual measurements cause no mutual interferences and the apparatus remains simple.
The coupling device preferably comprises several spring members, in particular springs, which movably hold the two reference members at a distance from each other with the desired number of degrees of freedom. In a simple and therefore preferred embodiment, several extension springs and a spacer member are e.g. provided. The spacer member is connected in articulated manner to one or both reference members, e.g. via ball-and-socket joints. Depending on the number of the desired degrees of freedom, the spacer member can be compressible along its length.
The device is preferably designed such that the possible mutual displacement of the reference members upon an actuation by hand is perceived to be comparatively large, i.e. that it is as least 1 centimeter or 20xc2x0 in each degree of freedom. Such displacements are distinctly perceived by a human user and allow a secure operation of the device.
The device according to the invention is especially suited as an input device for computers, a control device or a measuring device.